1. Field of the Invention
The present invention relates to centering devices, and more particularly to devices adapted to be mounted on well casings, liners, tubings, and similar conduit strings, for the purpose of centering such strings in well bores.
2. Description of the Prior Art
Centering devices having outwardly bowed springs are mounted on casing strings, or similar conduit strings, disposed in well bores for the purpose of placing and maintaining the casing strings substantially coaxially in the well bores. In some instances, the parts of said centering devices have been permanently assembled to one another at the point of manufacture, requiring the shipment in an assembled condition. In view of the large space or volume occupied by an assembled centering device or centralizer, substantial labor and material costs are entailed in boxing or crating it for shipment. Moreover, shipping costs have been comparatively high because of the large bulk or volume presented by the completed centering device, whether shipped boxed or unboxed. The large volume of the centering device also requires correspondingly large storage or warehouse space, which is costly to provide.
Conduit string centering devices have included end collars or annular members to which outwardly bowed springs have been welded. The welding operation entails the majority of time utilized in construction of the centering device. In prior art devices which have welding operations as a step in the manufacturing procedure, the completed apparatus oftentimes has resulted in a product which will enable the spring to give way during the transmission of the centering device within the well bore on the tubing or other strings because of the exteriorally affixed spring in relation to the collar element. That is, the spring has been welded to the exterior of the collar. Because the spring is outwardly flexed, and stress is exerted on the spring at the so-called "stress point", a break in the weld and/or the spring itself at the stress point will necessarily entail a break in the spring and/or a separation of the collar and spring, resulting in the spring being normally urged outwardly and away from the collar to the bore of the well, thus interrupting comparatively free travel of the centralizer mechanism in the well for setting. Additionally, breakage of the weld will prevent effective centering operation of the centering device.
Although non-welded centering devices have been offered by the prior art which have some advantages, particularly in view of the comparatively small amount of time and component parts utilized to assemble the devices, welded centering devices generally afford the most durable apparatus. However, because of the additonal manufacturing step of welding, heretofore welded centering devices have not been entirely successful.
Accordingly, it is an object of the present invention to provide an improved centering device or centralizer for well conduits that can be shipped to the point of use in a disassembled and compact condition, and then readily assembled at such point of use or at any other desired place, thereby effecting substantial savings in labor, material and time necessary for boxing, and in transportation costs, as well as in storage costs.
Another object of the invention is to provide a centering device or centralizer for well conduit strings that requires no particularly special equipment for its assembly. In fact, the parts of the present centralizer can be assembled by one or more relatively unskilled personnel utilizing a minimum of equipment and machinery.
A further object of the invention is to provide a centering device or centralizer for a well conduit embodying outwardly bowed springs adapted to be attached to associated collars or annular members by spot welding or otherwise permanently securing the parts to one another.
Yet another object of the invention is to provide a centering device for a well conduit in which the centering spring members can be assembled to the collars during a comparatively easy manufacturing procedure, and in which the springs remain properly assembled to the collars during normal handling of the device, during its installation on the well conduit, and during its running in the well bore. In addition, the construction of the well conduit centering device is such that in the event of a break in the weld of the spring to the supporting member, the spring is held in position and will not "pop out" of the supporting member. Therefore, the spring always will be in position to afford centering of the well conduit.
An additional object of the invention is to provide a centering device for a well conduit, the springs of the device being assembled readily by easy manufacturing applications in self-locking relation to the collars of the device, whereby disassembly of the device cannot be accomplished inadvertently.
It is a further object of the present invention to afford a method of assuring easy construction of the springs to the supporting members by providing support members which can be affixed to an inwardly and circumferentially extending shoulder upon each supporting member for resting of the respective ends of the spring members to assure further permanent securement of the spring to the support members.
It is a further object of the present invention to provide a well conduit centering device which provides a spring member welded or otherwise permanently secured to upper and lower supporting members, the weld or other permanent securing means of the spring to the support members being away from the stress point of the spring to provide additional strength in the spring and avoid weakness thereof by improper welding or other permanent securement.
It is a further object of the present invention to provide a well conduit centering device which will, upon failure of the weld or welds or other permanent securement, entrap the spring within the support member.
It is a further object of the present invention to provide a well conduit centering device having a flexing spring element, the flexing force of the spring not being carriable by the weld or other permanent securing means of the spring to the respective supporting members.
It is a further object of the present invention to provide a centering device for a well conduit embodying springs attached to collars, in which inward force or load on the spring tends to retain the attachment and assembled relation of the springs to the collars.
It is a further object of the present invention to provide a centering device for a well conduit embodying springs capable of ready assembly to associated collars, the assembled device being economical to produce, and being of strong and sturdy construction.
Other objects of the present invention will be apparent from a reading of the Figs., the specification below, and the claims.